1. Field of the Invention
The present invention relates to a camera, and more particularly to a structure for fixing an electric driving device for a camera to a camera body.
2. Related Background Art
For such structure there is already known, for example, one shown in FIG. 1, which is a cross-sectional view of a conventional structure for fixing an electric driving device for a camera to the camera body.
Referring to FIG. 1, an electric driving mechanism composed of a motor and gears is provided for film feeding, by transmitting the driving force of said motor and gears to a spool 1 thereby rotating said spool. A dust preventing member 30 is provided for preventing intrusion of dusts, such as broken pieces of the film, to a unit base plate 10, and also for preventing intrusion of oil etc. from said unit base plate 10.
Also a sprocket 2 is rotated by the meshing of the teeth 2a thereof with perforation holes of the film. The rotation is transmitted from a sprocket gear 3 to a sprocket conversion gear 4, and further to a sprocket limiting cam 5, a reversing prevention cam 6 and a phase detecting plate 7 rotating integrally with said sprocket conversion gear 4. The phase detection plate 7 is provided with a phase detecting switch 8 of which signal is used for controlling a motor 9 for film advancement.
The electric driving mechanism is integrally fixed on the unit base plate 10, which is fixed with a screw 13, either directly or through an elastic member 12 composed for example of rubber, to a camera body 11 formed by aluminum die casting or plastic molding.
However, such conventional structure has been associated with a drawback of noises and vibration from the motor and the gears becoming noticeable when the unit base plate 10 is directly screwed to the camera body 11. This drawback can be prevented by screwing the unit base plate 10 to the camera body 11 with a rubber member or the like therebetween, and, in the illustrated conventional example, the unit base plate 10 is screwed to the camera body 11 with an elastic member 12 provided therebetween.
On the other hand, the spool 1 is supported, as shown in FIG. 1, by the camera body 11 by way of a spool bearing 14, and, a certain gap has to be provided between the bearing 14 and the camera body 11, in consideration of the assembling procedure. Since no elastic member is provided in said gap, there inevitably results a positional aberration of the spool 1 relative to the camera body 11.
Consequently, even if the noises and the vibration can be alleviated by screwing the unit base plate 10 to the camera body 11 with the elastic member 12 therebetween, it has not been possible to secure the positional precision of the spool 1 relative to the camera body 11. Such drawback is not limited to the spool 1, but a similar drawback is associated with the sprocket 2.
This fact leads to another drawback which is explained in the following. The camera body is generally provided therein with an exposure aperture for exposing the film to the light, and it is not possible to maintain the positional precision of the spool 1 and the sprocket 2 relative to said exposure aperture, once a positional aberration is involved in the sprocket 2. As a result, the stopping position of the film can no longer be made constant, and the gap between the image frames on the film inevitably fluctuates.